Hair animation is difficult primarily due to the large volume of hairs considered (a typical human head consists of 100,000 hair strands) and the complex hair motions and interactions. Despite this, there has been enormous success in model acquisition, simulation, and rendering of hair (e.g., Rapunzel's hair in the movie Tangled®). Such high-quality simulations, however, are expensive and generally require off-line processing, in the range of minutes per frame. Real-time applications, such as prototyping and games, have more stringent computational budgets, and hence often rely on less realistic models which are either entirely procedural, topologically constrained, or approximate simulation using low-resolution models.